A general mobile robot employs a step motor for moving to a desired destination. In order to reach one point and then move toward another point, such a general mobile robot is turned to a desired direction by controlling the rotation number of the motor and is then moved by a predetermined distance by a driving motor controlled by a microcomputer.
Alternatively, in order to return to an original position (i.e., a started position), the robot must be moved from the reached position toward the original position by using the rotated numbers of the step motor and the driving motor, the rotated numbers being stored within a memory means in the microcomputer at the time of the initial movement.
In such a method for moving the robot as described above, however, when the robot is moved from one point toward another point, a moving course is determined based on the rotated numbers of the step motor and the drive motor. This prevents a determination of a relative moving vector between the initially started position and the presently reached position. For this reason, when the robot is returned to the originally started position after the robot has been moved to any point, the robot must be repeatedly moved back along the course previously moved. Therefore, the conventional mobile robot has a problem in that the robot cannot be returned along the shortest distance. Also, the moving direction of the robot is only determined based on the rotated numbers of the step and drive motors, so that if the rotated numbers of the robot are changed due to, for example, the friction resistance of a drive mechanism or an obstacle, etc., and the robot is deviated from a desired moving course, this state cannot be determined, whereby the deviated value from a normal moving course cannot be readily corrected.
In addition, in the mobile robot, the step motor is used as a means for precisely determining the direction and for controlling the distance, thereby causing a problem in that the manufacturing cost is increased.
A concrete example of a conventional mobile robot is disclosed in U.S. Pat. No. 4,638,445. This conventional robot is shown in FIG. 1 and includes a vision system 31; a memory means for storing data entered from the vision system 31; and a computer for processing data entered from the vision system 31 of the robot. The robot includes a first transducer array 34 which is symmetrically disposed with an axis of symmetry of the mobile robot 30 for obtaining data relative to the position and the distance of an object in a workspace; a second transducer array 35 which is symmetrically disposed with the axis of the robot 30 but along a different angle relative to the first transducer array for obtaining data relative to the position and the distance of an adjacent object in the workspace; means for sequentially transmitting signals determined by the computer 33 to each of the transducers; and, at least one auxiliary range transducer 36 for obtaining the position and distance information of the object deviated from the visual ranges of the first and second transducer arrays 34 and 35.
With this construction of the robot, there is an advantage that all of the obstacles encountered in the work space can be precisely and effectively measured since the rotation of the robot is controlled using data information processed through software built in the microcomputer. However, the plurality of transducers of which the sensing areas are different from each other are disposed in two columns over the whole periphery on the top of the mobile robot where the auxiliary range transducer is also disposed, thereby causing a complicated construction and a high manufacturing cost. Furthermore, the software built in the computer which determines the moved distance and the rotative state is complicated because of the plurality of transducers. If an erroneous operation occurs, the robot will deviate, thereby making it is impossible to protect the device from damage and to prevent such an accident.